As part of the DEEP permit process, the lake authority will have to find ways to keep the carp in Candlewood and not allow them to swim down the outlet pipes to the Housatonic River.

The authority will have to find a way to pay $50,000 to buy the fish.

More Information

About the grass carp
(Ctenopharyngodon idella)
Native to China and Russia
Members of the minnow family
Related to goldfish
Dark gray to golden brown on the back, white on the belly
Feed strictly on aquatic vegetation
Introduced to about 50 countries worldwide because of its ability to control nuisance plants
Source: New York Department of Environmental Conservation

"That's what we still have to work on,'' Larry Marsicano, the authority's executive director, said Wednesday.

But Marsicano said given the problems that authority has had in recent years in controlling watermilfoil, a non-native invasive aquatic plant that clogs the lake's bays and inlets, the carp may need to come to the rescue.

DEEP spokesman Dennis Schain said Wednesday that sterile grass carp have been used successfully in small ponds in the state, including Ball Pond in New Fairfield.

"It's something worth considering,'' Schain said.

Cynthia Stevens, chairman of the Ball Pond Advisory Committee, said the panel was the first to use the sterile fish to control watermilfoil. It started in 1997 with 412 fish, she said, and the 246-acre Ball Pond has been regularly restocked since then.

The committee adds about 75 carp every two years, and the fish have done the job they were hired for, Stevens said.

"We've gotten rid of the watermilfoil,'' she said.

The Candlewood Lake Authority has controlled the watermilfoil in the lake by winter drawdowns, lowering the lake each winter to let freezing temperatures kill the plants left exposed on the lake's mud flats.

But this strategy has proven less effective for a variety of reasons, including shorter drawdown duration and winter weather that has failed to kill the plants.

"We've seen the weather get a little crazy,'' Marsicano said.

In 2012, the watermilfoil growth got so thick on the lake that the authority decided to consider other methods of controlling the weed.

Marsicano said using herbicides, along with being controversial, is expensive, costing about $200,000 a year. Using the carp, he said, seemed like a biological control that might be a better alternative.

The carp eggs are treated in a hatchery to render the fish sterile. Therefore, they won't breed and reproduce.

Because they're weed-eaters, the carp don't compete with other species of fish, including Candlewood Lake's prized bass, Marsicano said.

They also eat weeds from the top down, allowing more light to get into the lakes where they live. That allows native plant species -- overshadowed by the mats of watermilfoil -- to rebound. It also means the swimmers and boaters -- who use the top layer of the lakes -- benefit early from the carp.

"They're like lawn mowers,'' Stevens said.

Grass carp are chow hounds that can grow to 25 pounds or more, according to the New York Department of Environmental Conservation. They live for about 10 years, but feed the heaviest in their early years. That means they have to be restocked every few years to stay effective.

The carp can have unexpected consequences. At Ball Pond, with the watermilfoil gone, a brushy native aquatic species, called coontail, is flourishing. The Ball Pond Advisory Committee wants to add more carp into the lake to tackle the new nuisance.

"We've been stocking 75 fish every two years,'' Stevens said. "We want to go up to 175.''